Interactive sound propagation has emerged as a powerful tool in computer graphics to enhance the realism of virtual worlds by predicting the behavior of sound as it interacts with the environment. In order to generate realistic acoustic effects, including interference, diffraction, scattering, and higher-order effects, it is important to develop techniques that can directly solve the acoustic wave equation. There is extensive work on numerical methods in scientific computing and acoustics to solve the wave equation. Furthermore, there has been considerable interest in developing interactive wave techniques such as modeling free-space sound radiation [James et al. 2006], first-order scattering from surfaces [Tsingos et al. 2007], and performing sound propagation for indoor scenes [Savioja 2010; Raghuvanshi et al. 2010].
Large open scenes, which arise in many applications ranging from games to training/simulation systems, present a significant challenge for interactive wave-based sound propagation techniques. State-of-the-art wave simulation methods can take hours of computation and gigabytes of memory for performing sound propagation in indoor scenes such as concert halls. For large, open scenes spanning hundreds of meters, it is challenging to run these techniques in real-time. On the other hand, geometric (ray-based) acoustic techniques can provide real-time performance for such environments. However, geometric techniques are better suited for higher frequencies of the audible range since accurately modeling diffraction and higher-order wave effects remains a significant challenge, especially at low frequencies.